The present invention relates to a supporting device of magnetic heads for recording and reproducing information on a virtually transparent magnetic layer (referred to as a transparent magnetic layer, hereinafter) provided on a photographic film.
Recently, the performance of individual units composing a photographic system such as films, cameras and photo-finishing machines has been remarkably improved. However, photographic information can not be sufficiently exchanged between them. Therefore, it is difficult to further improve the performance and to reduce the costs and time. For example, according to the present color printing system, the camera conditions and the object informations are presumed from the optical data of a developed negative image, and then the printing condition is determined only on the basis of the presumed data. Under the above printing condition, printing operations are conducted so as to meet the requirements of average customers. Accordingly, the printed photographic images are in a average level, so the photographing conditions and the purpose of photographing are not fully reflected on the prints. For this reason, the performance of films and cameras can not be fully utilized. In order to meet the requirements of users, it is necessary to incorporate photographic information into printing operations.
However, the photo-finishing operation is conducted in a water solution and in a dark room, it is difficult to transfer information to photo-finisher from customer.
In the International Application Nos. WO-90/04205 and WO-90/04214, and U.S. Pat. Nos. 4965627 and 4975732, a means for easily exchanging information in a photographic system is disclosed, in which a transparent magnetic recording layer is coated all over the back surface of a film and necessary information is directly recorded on the film. That is, when a film is manufactured, a manufacturer's name, type of film, lot number of emulsion, sensitivity, date of manufacture, reference signal, and the like are recorded on the film. In the case of photographing, the following photographing conditions are recorded for each frame: color temperature of a light source, luminance level of an object, shutter speed, aperture size, backlight control, rapidfire mode, type of camera, photographer's ID, photographing date, and memo written by the photographer. Further, when the film is received by a photo finishing-laboratory, the following customer's orders are recorded on the film: a printing size, number of prints, and type of surface finish (silk-finish or luster-finish). In the printing operation, the recorded information is read out from the film, and the printing condition is determined based on this information together with the optical data obtained when the negative film is been scanned. In this way, the photographing conditions and photographing purpose can be fully reflected on the print. When these photographing conditions are recorded in each frame of the film and read out in the printer, a print of equal picture quality can always be obtainable. Since various information of photography can be directly recorded in each frame as described above, it is possible to automatically control the printing operation with a computer, so that the following advantages can be provided. They are a improvement in picture quality and reduction in cost and processing time. This system is characterized in that: since the photographic information is directly recorded on a film, the information completely corresponds to each frame; and when a signal modulation system insensitive to the fluctuation of the film transport speed is employed, these recorded information can be easily transferred.
In order to record photographic information, not only magnetic recording means but also electrical or optical means can be employed. The electrical means in which IC memories are used are disadvantageous in that the costs are high. The optical means in which bar code system are used are also disadvantageous in that the recording capacity is small and it is impossible to rewrite the information. For this reason, the magnetic recording method by which photographic information can be directly recorded on a film is most appropriate because the recording cost is low, the recording density is high, the recorded information can be arbitrarily rewritten, the photographic information completely corresponds to an image in each frame, and the photographic information can be easily transferred.
In general, conventional magnetic recording is conducted in the following manner: a signal current is made to flow in a coil of a magnetic head (referred to as a head, hereinafter); and a generated magnetic field magnetizes a magnetic layer on the film. In the case of reproduction, leakage flux from the magnetic surface is picked up by the head core. Intensity of leakage flux generated from the surface is very low, so that the range of the magnetic flux is very narrow. Therefore, when a small spacing exists between the head and the magnetic surface due to an poor contact, the output level is greatly lowered and the signal can not be completely reproduced, which leads to a serious data error. Consequently, the intimate surface contact between film and head is very important. In the case of magnetic recording, a track is provided on the recording medium and signals are recorded on the track. Unless the reproduce head can precisely traces the track, the output level is also greatly lowered. Therefore, tracking is very important, too. Further, the medium is magnetized by the leakage flux from a gap of the recording head, and a gap of the reproduce head picks up the leakage flux from the medium. Therefore, an angle of the recording gap and that of the reproducing gap must be the same. Even when a offset between the head gap angles is about 1 degree, the outputs level is considerably lowered. This is referred to as an azimuth misalignment loss, and it is important to minimize the misalignment loss. In general, the conventional magnetic recording medium is filled with magnetic material at high density, because the output level depends largely on the packing density of the magnetic material. In the conventional magnetic recording apparatus, the transport speed and the track position of the medium must be strictly controlled. In summary, a good head contact, a precise tracking, a strict speed control and low azimuth loss, are the indispensable conditions for the conventional magnetic recording. On the other hand, the present application in which photographic information is directly recorded on a magnetic layer of a film is completely different from the conventional magnetic recording. For example, in the case of a photofinishing apparatus, we can not expect to control the transport speed and tracking position so strictly as the conventional magnetic recording apparatus. Further, in order to ensure the transparency of a film, an amount of magnetic material of the magnetic layer coated on the film is limited about 1/50 to 1/100 of a conventional magnetic recording medium, so that output signal level from the film becomes very low. In the case of a conventional magnetic recording medium such as a audio tape filled with a large amount of magnetic material, the output level is high enough, so it is less sensitive to head contact, tracking and azimuth loss. However, in the case of the present application, a transparent magnetic layer is employed, the output of which is about 1/50 to 1/100 as low as that of conventional magnetic medium. Therefore, the output signal level is largely affected by the head touch, tracking or azimuth misalignment. As described above, when signals are recorded on the transparent magnetic layer, it is very important to keep a good head touch, a precise tracking and a correct azimuth angle. However, the photographic film is stiffer, thicker and more curled than the conventional magnetic tape. Consequently, poor head touch, off tracking and azimuth misalignment tend to occur on the film easily. Further, the speed and tracking control of the photographic apparatus is much less sophisticated than that of a conventional magnetic recording apparatus. As described above, it is very difficult to record or reproduce information on the transparent magnetic layer of the photographic film.
A comparison between the conventional magnetic recording and the magnetic recording of the present application on the transparent magnetic layer provided on a film, will be made and problems caused during recording and reproducing will be explained as follows. In this case, the transparent magnetic layer is very thin (not more than 1 Jm, and preferably aroud 0.1 Jm), so that a ratio of the magnetic layer on the film is small. Accordingly, explanations will be made on the assumption that the physical properties of a film provided with the transparent magnetic layer are substantially the same as those of a conventional photographic film.
In general, a magnetic tape is made of a thin base film and a soft binder such as polyurethane so that the head and tape can easily keep good contact.
On the other hand, a photographic film is made of a base film, which is 5 to 10 times as thick as that of the magnetic tape, and a hard binder such as gelatin, so that a film cannot keep good contact with head. Therefore, a film is much stiffer than a magnetic tape and lacks the flexibility. Also, a film is composed of several of tens layers including a subbing layers, photosensitive layers and protective layer coated on the base film, so that the construction of the film is very complicated. Although an anti-curling layer is provided on the opposite side of emulsions, the layers become unbalanced during processing, and the film is considerably curled. Further, it tends to curl due to the variation of temperature and humidity. In this way, the film is curled in both the lateral and longitudinal directions. When the curls of these directions are combined, an irregular deformation is caused on the film surface.
As the transparent magnetic layer is coated all over the film surface, recording is possible on the entire surface. However, it is preferable that information is recorded in the non-image area on the film surface located in ranges within about 5 mm from the film edges. In the magnetic recording, the recording density is high, so that the information can be sufficiently recorded in these regions. In general, a photographic film curls in the lateral direction being formed concave while the emulsion layer surface is located inside of the curled surface. Especially, the edge portions are considerably curled. Therefore, it is difficult to obtain a good contact condition of the head in the curled edge portions.
What is called a magnetic film in which a thick magnetic layer is provided on a photographic base film, is used for recording sound in a motion picture. This film is also stiff and is difficult to obtain a good head contact, however, this film is used for sound recording only. Unlike the film of this invention, an amount of magnetic material to be used is not restricted. Therefore, an amount of magnetic material several times as much as that of the conventional magnetic tape is used so as to obtain an excellent S/N ratio. For this reason, a high output can be provided, so that the magnetic film is not so sensitive to a head touch, tracking and azimuth misalignment as the film of this invention.
As described above, it is very difficult to record or reproduce information on a film having a transparent magnetic layer compared with a case in which a conventional magnetic recording is conducted. According to the present invention, a new magnetic head supporting device is provided so as to solve the problems.
A magnetic head supporting device used for photographic films is disclosed in U.S. Pat. Nos. 5034836 and 5041933. According to the above patents, the magnetic head supporting device is constructed in the following manner: Two film guides to which the magnetic heads are attached, hold both edges of a film. An entire head unit is moved on an arc in accordance with the fluctuation of a film running angle, and several ball bearings are provided so that the heads can trace the irregular movement of the film edges. The above inventions solve the problems of tracking offset caused by the irregularity of the edge and variation of film width.
On the other hand, the present invention solves the problems caused by curling and deformation of the film. Further, the present invention solves the problems of defective edges, defective splice, change in the film angle, and irregularity of the reference edges. Furthermore, the present invention solves the problems of an film running, such as rolling and meandering. In the construction of the present invention, a number of leaf springs are combined, so that a transportation shock transmitted from the film can be effectively absorbed, which is unlike the construction in which a number of bearings are used.
A large number of problems which can not be solved by the conventional technique are encountered in the case of recording and reproducing on a film having a transparent magnetic layer. For example, the conventional magnetic recording technique in which a magnetic recording medium is pressed against a fixed head surface so as to obtain a good contact condition, is commonly used, however, in the case of a stiff and considerably curled film, the above technique can not be applied. If the film is strongly pressed against the fixed head surface, it is possible to keep a good contact between them. However, the signals are not stable and the film surface is easily damaged by the head. Since the transparent magnetic layer is coated all over the film surface, and recording is possible even in the image area, the damage of a film can be a fatal problem. Further, when the head is strongly pressed against the stiff, curled film, the head wears out quickly. A poor contact between the head and the film also causes various signal noises. Since the low output level signal must be amplified by an amplifier of high gain, the noises are also highly amplified, and the signal quality is largely deteriorated.
The present inventors have succeeded in obtaining a good and stable contact by using tiltably rotatable head support instead of fixed support. When the head and film are contacted, the film is deformed by the head and at the same time the head is tilted by the film. Therefore, the heads and film can quickly come into good contact with lower contact pressure, and the film surface can be prevented from being damaged and also the head surface can be prevented from wearing out. Since excessive head wear can be avoidable in this case, not only an expensive hard material difficult to be machined such as Sendust (Al--Fe--Si), but also an inexpensive soft material easy to be machined such as Hard Permalloy (Fe--Ni) can be applied for the head. However, the tiltably rotatable heads have some disadvantage. When the head angle is changed tracing the curls of the edge portions, partial off tracking may occur. However, when a head is tiltably rotated with a center at the track center, the head can trace the track without causing off-tracking.
In the magnetic recording on a film, film edges are used as a reference and tracks are provided at a position separated by a predetermined distance from the reference edges. In order to obtain interchangeability, the position and width of these tracks must be standardized. In the case where a magnetic trackrecorded by a camera is read out by a head of a photo-finishing machine, it is necessary that the tracks must be precisely traced by the head of the photographic printer. Since the photographic film is harder, thicker and more curled than the conventional magnetic tape, it is difficult to accurately slit the photographic film and the width of the film can fluctuate and edge irregularity can occur. So,the reference edges of the film tend to fluctuate. When the photographic films are processed, a large number of roll films are spliced so as to be formed into one big roll, and then the big roll is continuously processed. When the films are spliced with a splicer, the films can not be connected accurately, and a number of discrpancies can be caused. For this reason, the reference edges can be deviated after the splicing operation. Commonly, the width of the magnetic track is below 1 mm. When a discrepancy of 1 mm is caused between the films in a splicing portion, a head is completely deviated from a track. Unless the films are spliced linearly, the reference edges are gradually deviated. As described above, the slitting and splicing accuracy of a film are much lower than that of a magnetic tape. Consequently, the head supporting device must quickly follow the change in the reference edges position.
The film transport system of the photo-finishing apparatus is not sophisticated enough and the film is fed intermittently for each frame in the printer. Therefore, the film feeding speed is suddenly changed and the film is swayed laterally. Accordingly, poor head contact, off-tracking and azimuth misalignment tend to occur. For this reason, it is necessary for the head supporting device to be able to compensate this change in the film edge positions.
According to the present invention, the problems related to the tracking operation can be solved in the following manner: A film guides engaging with the reference edges of a film at all times are provided. A supporting member is integrated with this film guide and a head is attached to this supporting member.
Also, the film is held between one set of film guides. Even when the film angle or film position is changed due to edge irregurality, fluctuation of the film width, lateral sway of the film or defective splice, the entire head unit can compensate the fluctuation, so that an angle and position of the reproduce heads are maintained to be a predetermined value at all times, and the occurrence of an off-tracking and azimuth losses can be avoided.
When signals are recorded on a magnetic recording medium, it is necessary for the head to closely come into contact with the film surface. However, when the head is moved following the film, an angle formed between the head and film surface is changed, so that a spacing is formed between the head and film surface. As a result, the signal output is lowered, which causes an error.
The present invention relates to a magnetic head supporting device in which an angle formed between the surfaces of the head and film is always maintained zero even when the head position is moved. According to the magnetic head supporting device of the present invention, even when a positional relation between the film and head is greatly changed, the head can trace the movement of the film without forming any spacing between the head and film surface, and signals can be precisely transferred.
When the head is supported by a springs, there is a possibility that the head is vibrated by the action of friction. However, strong springs are utilized so as to prevent the vibration of the springs, wherein the springs are composed of a trapezoid spring and parallel spring which are combined, and these springs are activated so as to compensate each other. According to this head supporting construction, the head can trace the film surface smoothly and quickly. Also, these springs absorb a shock transmitted to the head from the film. Therefore, the sway of the head can be avoided, the output signal can be stabilized, and As a result, the reliability can be improved.